How can I manage hypotension in a patient with Hypertrophic Obstructive Cardiomyopathy (HOCM)?

Managing Hypotension in HOCM Patients

For acute hypotension in patients with Hypertrophic Obstructive Cardiomyopathy (HOCM), intravenous phenylephrine or another pure vasoconstrictor is recommended as first-line treatment, combined with fluid administration to maximize preload.

Pathophysiology and Principles

Understanding the unique hemodynamics of HOCM is crucial for managing hypotension:

• In HOCM, hypotension can worsen left ventricular outflow tract obstruction (LVOTO)
• The goal is to maintain or increase preload and afterload while avoiding increases in contractility or heart rate
• Reduced preload (from vasodilation or hypovolemia) exacerbates LVOTO
• Increased contractility (from inotropes) worsens LVOTO

Acute Hypotension Management Algorithm

First-line interventions:

1. Fluid administration to increase preload 1

   • Administer IV fluids to restore intravascular volume
   • Monitor response carefully to avoid fluid overload

2. Pure vasoconstrictors 1

   • Intravenous phenylephrine is the agent of choice
   • Titrate to achieve adequate blood pressure
   • Beta-blockers can be used in combination with vasoconstrictors to dampen contractility

Avoid these agents (Class III: Harm):

• Positive inotropes (dopamine, dobutamine, norepinephrine) 1
• Vasodilators (nitroglycerin, dihydropyridine calcium channel blockers) 1
• Diuretics (in high doses) 1

Chronic Management of Blood Pressure in HOCM

For long-term management of blood pressure in HOCM patients:

First-line agents:

• Beta-blockers 1
  • Titrate to resting heart rate <60-65 bpm
  • Reduce contractility and improve diastolic filling
  • Examples: metoprolol, propranolol, atenolol

Second-line agents:

• Non-dihydropyridine calcium channel blockers 1
  • Verapamil (up to 480 mg/day)
  • Diltiazem
  • Use with caution in patients with high gradients or advanced heart failure

For refractory cases:

• Disopyramide combined with beta-blockers or calcium channel blockers 1
• Mavacamten (cardiac myosin inhibitor) for adults 1
• Septal reduction therapy in eligible patients at experienced centers 1

Special Considerations and Pitfalls

• Avoid vasodilators that can worsen LVOTO:

  • Dihydropyridine calcium channel blockers (nifedipine)
  • ACE inhibitors
  • Angiotensin receptor blockers
  • Nitrates

• Use diuretics cautiously 1:

  • Only low doses when absolutely necessary
  • Monitor for worsening obstruction due to decreased preload

• Verapamil is potentially harmful in patients with:

  • Severe resting obstruction (gradients >100 mmHg)
  • Systemic hypotension
  • Severe dyspnea at rest 1

• Consider extracorporeal life support in refractory cases during surgery 2

By following these principles, hypotension in HOCM patients can be effectively managed while minimizing the risk of worsening outflow tract obstruction and associated complications.